The technical field of invention relates to a current measuring device for measuring an electric current running through a conductor. More particularly, the present invention pertains to a hand-held hook-ended slide closure electronic current measuring device for measuring an electric current running through a conductor by detecting the magnetic flux generated by the electric current.
Non-contact, non-interrupt current measuring instruments are used in numerous applications where a conductor to be tested is live and cannot be electrically disrupted. Such applications are common, for example, in factory or office power distribution systems. Reliable and efficient means to measure current passing through an electrical conductor (or wire) without disconnecting the conductor or without direct electrical contact with the conductor have been attempted with varying degrees of success by different types of current measuring devices.
Perhaps the most common hand-held current measuring devices are of the clamp-on or hook-on type. Some brands of clamp-on current measuring devices are referred to as hook jaw type current measuring devices. All of these devices comprise a substantially circular clamping ring wherewithin a conductor may be positioned by opening a section of the hinged clamping ring, positioning the clamping ring around the conductor, and finally closing the clamping ring whereafter a current flowing through the conductor, typically an alternating current, may be measured. Such devices are available in a wide variety of sizes and with various sensitivities. However, clamp-on type current measuring devices incorporate hinged mechanisms for opening and closing a clamping ring (or core). Further, users of conventional clamp-on type current measuring devices have indicated that the hingeably open clamping ring is too large to fit around conductors when working in smaller spaces such as junction boxes, distribution panels, or similar electrical system enclosures. The conventional clamp-on type device requires the user to have enough space to hingeably open and then close the clamping ring around the conductor in order to make a current measurement.
U.S. Pat. No. 6,456,060 by Wiesemann and U.S. Pat. No. 5,349,289 by Shirai are each directed to hand-held clamp-on type current meters. Both include a side lever mechanism for hingeably opening one side (or jaw) of a clamping ring which, when depressed, allows for insertion of a conductor into an area enclosed by the clamping ring. Other clamp-on type devices, such as the clamp-on device disclosed in U.S. Pat. No. 5,610,512 by Selcuk, include a side lever mechanism that operates to hingeably open two hinged halves of a clamping ring. Yet another clamp-on type device, disclosed in U.S. Pat. No. 6,541,955 by Landre, uses a pliers type mechanism for hingeably opening two halves of a clamping ring. Each of these exemplary clamp-on type current measuring devices include a hinged clamping ring that is opened for insertion of a conductor to be tested and closed to allow for a current measurement.
An alternative to the clamp-on type current measuring device is a hand-held open fork type device that uses a C-shaped or horseshoe-shaped core wherewithin a conductor may be positioned for measuring an electric current passing through the conductor. U.S. Pat. No. 6,586,923 by Seike and U.S. Pat. No. 6,043,640 by Lauby et al. are each directed to hand-held open fork type current meters. Such open fork type devices require the user to either extend the device forward to position a conductor under test into the interior area within the C-shaped core or to bring the conductor rearward and into the interior area in order make a current measurement. Open fork type devices may be less bulky and easier to use in certain applications than the conventional clamp-on devices. However, open fork type devices are less accurate due to current leakage associated with what is effectively an open jaw when taking measurements, and open fork type devices still require undesirable manipulations in many routinely encountered situations.
For example, unlike the use of clamp-on type devices whereby a conductor under test may be isolated by closing the jaws or portions of the core (ring) around the conductor, thus affirmatively isolating the conductor, isolating a conductor with an open fork type device may require that the user reach with a free hand into the space occupied by the conductor in an effort to pull the conductor into the C-shaped core area so that a current measurement may be attempted. In typical applications, such manipulations may need to be repeated frequently, especially where several conductors are aggregated or bundled together in an electrical system access panel, junction box, distribution panel, or similar enclosure commonly used in wiring systems.
A novel and effective improvement is described in U.S. Pat. No. 7,327,133, filed May 4, 2006 and granted Feb. 5, 2008 (hereinafter, the '133 patent or, simply, '133), which is hereby incorporated by reference herein in its entirety. The '133 patent discloses a handheld-sized current measuring device including a probe body having an elongated portion extending outward to a hook-shaped end useful for isolating a conductor under test. However, the '133 device shares a disadvantage of open fork type devices—that is, the open end where the conductor under test is positioned for measuring current does not include structure or mechanisms for capturing the conductor.
What is needed is a current measuring device that provides a user with improved convenience and utility for various applications, especially for applications where the user may be required to work within tight spaces or spaces having several conductors bundled closely together. What is needed, therefore, is a different style of current measuring device.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.